Harman Kardon A402 restoration (Ep. 1)

[@ClausHensingDenmark]

Thanks Trevor - your restoration/repair-videos are very useful and inspiring. Also I like that you take your time and doesn't edit each project down to 5-10 minutes - and that you are not to "proud" to show that even a pro can make a small mistake. I have several H+K models (430c, 730, 402, 403, Citation 17, 18 and 19) which all could benefit from a renovation so I'll definitely use your videos to help me. Thanks!

[@TrevorsBench]

Thanks for the kind words Claus. It's nice to know that someone might find my videos helpful

[@tinagladu3744]

trevor you really restored that one nice instead of it being trashed,good to see and good job

[@TrevorsBench]

Thanks Tina, I love this amp and will take it to my grave. Has to be in the top3 for best sounding, IMO

[@JamesHowe]

I still have my A402 but I haven't used in in years. Many years ago I had to have it serviced a handful of times because one of the channels kept cutting out. The repair people always told me they fixed "bad solder joints". When it worked properly it was a great amp. I paired it with some Klipsch Heresy speakers and the 40 watts/channel was plenty.

[@TrevorsBench]

Nice. The channel cutting out is a common fault for the A402. There are board interconnects that are tin plated and over time they oxidize and make flaky connections. I made a followup video about this. I bet sounded great with the Heresys, the A402 is known for it's tight bass

[@lenageeraerts6364]

Thanks, very pleasant video............ I have two of them to restore. These amplifiers sound really good.

[@TrevorsBench]

You're very lucky to have two. After I did the full re-cap I was amazed at the clarity of the sound this amp delivers

[@brianwood5220]

Great video thanks Trevor.

[@tornadosilver6330]

Trevor. Liked the video but I do not have the knowledge or equipment to repair/refurb my 1977 HK 730. Do you do for hire?

[@TrevorsBench]

The 730 is a nice unit. I have one on my bench right now getting a restoration, video to follow in January. I do hire for locals. The cost of shipping and the risk of damage is too great for most people. I'm in Alberta Canada. I'm not sure where you are but typically I don't take on work from outside of my local area Thanks for asking tho

[@hartzhockey]

Hi, great videos. Thank you. I just had a question. My A402’s power cord was getting pretty dry rotted. I am going to replace the power cord with a 3 prong cable. My question is the negative of the power cord tied to the green wire or the gray wire where it ties into the unswitched AC input? Thank you. Geoff

[@clementbruni8413]

Hello, I recently bought a HK a402 and i am looking for new switches for the LED panel. Unfortunatly, all button are broken, despite the switches are fine. Do you know what is the reference on digikey ? I dont know anything about eletronic :s Thanks for your answer !

[@TrevorsBench]

The part numbers are in the video description. They will need to be modified and fitted to the latching mechanism in the LED panel. It can be done.

[@JerryPemberton]

Didn't you have a link for replacement push buttons? Or are they in the follow up video?

[@TrevorsBench]

Hi Jerry, I updated the video comment to have the part numbers

[@JerryPemberton]

@@TrevorsBench Thanks!

[@emrelsd]

Hello Trevor! I begin restoration of my HK730 recently and your videos have been really helpful. Especially bias alignment: for an amateur like me close ups and detailed videos help a lot: just like school but even more fun.. And I have a question: You mentioned the "new signal switches" where do you buy those and what are the specifications?

[@TrevorsBench]

I've listed switches in the description above. They are not a perfect fit, they will need some modification to work

[@artboelke5721]

I have a HK A402 and think it is one of the best sounding amps I have . I have bought all the electrolytics to recap but it sounds so good I have put it off. One of the items I have not seen on the schematic is a DC offset adjustment pot. Nor have I seen a protection relay circuit. Is the soft start circuit suppose to add dc current protection? I think its for current inrush limiting and not DC current elimination. If that is the case is there any protection in this receiver? Please comment. PS ..Love all the vids. I learn from them.

[@OffTrackProductions]

The tone defeat switch is acting up on mine. Right channel cuts out unless the switch is held in. Hoping I can just drench it in contact cleaner and that will fix it. But if not, may have to follow your steps here. Great video.

[@CoryHuber]

I have the same model with a scratchy left channel. I hooked the pre-amp up to a separate amplifier and it sounds clear. I listen on headphones and it's clear. It's gritty sounding on only the left channel with both Speaker A and Speaker B. Do you have any idea what might be the cause? I'd love an expert opinion on how I might get this beautiful machine back onto the shelf playing sweet music. Thanks Trevor!

[@tommyblanford9974]

I have found both the A402 and T403 and have purchased them for my son as a college graduation present. The are both in cosmetically very good shape but would like them both gone through and refurbished for him-would you be interested?

[@TrevorsBench]

I appreciate the offer but I'm not in a position to take on the extra work. My local clients keep me very busy. Sorry

[@stephenrejto8784]

Wow - amazing job. I have a unit that I have been using. After 20-30 minutes sometime the right channel cuts out. If I wait and restart it, it comes back. I dont have your talent (or equipemtn) for a full rebuild, but could certainly probe a few spot and replace a few caps. Any reccomendations fo where youd'd look? I was hoping for a cold solder joint but dont see any. Thanks again for an incredible video

[@TrevorsBench]

Hi Stephen and thanks. If you've got a channel cutting out I would check the interconnects between the boards. They used tin plated connectors which work fine for the first 20 or so years then they start to get flakey with age. You're pretty safe to remove the cover and wiggle the boards to find the poor connection. Mine had a dirty connector behind the hinge switches connecting to the preamp board I have a video coming up fixing this

[@francoislevy8159]

Thank you so much for this video. I have exactely the same problem with the switches, and I would like to change them. Could you please give us the references of the new gold and silver switches you used?

[@TrevorsBench]

Hi and thanks. Digikey sells the switches that will fit with minor modification. Silver switches must be used for the speakers and the rest of the signal switches can be replaced with gold plated. Go to digikey and search for F4UEE-Au, F4UEE-TB, F2UEE-Au

[@JerryPemberton]

@@TrevorsBench Which of the three replacement buttons go in place of which existing buttons? Also, do these replacement buttons sell for $10 each? So, we're looking at about $110 for the new buttons?

[@TrevorsBench]

@@JerryPemberton I can't remember off the top of my head. If you go to www.hifiengine.com/ and download the service manual it shows which switch goes where. The speaker switches must be silver plated, the rest can be gold plated

[@bogie1971]

Is it for sale? I want it lets make a deal are you in Florida??

[@TrevorsBench]

Sorry, this one's not for sale